Collision not working
It seems the only way the player collides with the walls is because go that small white box. You could either get rid of the box and just use the character, or stretch the box upwards so it collides with the walls on top too, although this may be unnecessary.

To make the restarting game properly work, you the game property called 'obs' should be set to boolean and 'True'. Also, delete the sensor for the collision with the property of 'prop'.